U.S. Pat. No. 4,474,717 describes an injection of a small portion of plastics without introducing inert gas (preloading) followed by sectional introduction of inert gas using frequencies from 4 to 100 cycle per second having a pressure of 300-1500 psi (2 to 10 MPa) into the continuous passing plastic material. The result is a multi-layered internal foamed structure. The present invention expands this method by applying injection technology used in the combustion engine technology and reaching a more intensive penetration by higher pressure (40 to 200 MPa), higher frequency (100 to 1000 hz) and more exact dosing by controlled width of the pulses, frequency of the pulses and regulation of pressure using this technology.
The pulsing adding of liquid and gas is state of the art in burner systems, airless jet systems and spraying systems (atomizers). The present invention is distinguished from these applications by higher pressure of the liquid than 40 MPa and high energy atomizing. This pressure is not possible with the nozzles used at this time. Only by electrical activated hydraulic servo valves in common rail technology can these pulsations be realized.